0.6
 - Major rewrite to support configurable and reusable handles
 - Added new_handle, handle_setopt, handle_setheaders, handle_setform, handle_reset, etc.
 - Added curl_fetch interfaces for httr
 - Add ie_proxy_settings to get system proxy configuration on windows

0.5
 - Check for CURLM_CALL_MULTI_PERFORM to support very old versions of libcurl

0.4
 - Fixed a memory bug that could cause R to crash
 - Add curl_escape, curl_unescape
 - Add curl_version and curl_options

0.3
 - Add curl_download function
 - More efficient use of realloc
 - Fix for older versions of libcurl (e.g. Snow Leopard)
 - Add support for user interrupts while downloading (ESC or CTRL+C)
 - Fixed bug that caused GC to corrupt connection object
 - Refactoring and cleanup

0.2
  - add support for recycling connections

0.1
  - initial release
